Some time ago I was browsing through list of orphaned Debian packages1. and encountered filter program with very promising description — “filter is one of the original mail filtering programs written for UNIX”.
It is much simplier than procmail, its manual page is page, not manual, while supporting almost anything I need:
regex/substring matching of Subject, To and From headers
built-in delivery into mboxes and any other develiery method via piping. It is important to me, since I use mmh2 mail user agent, which uses its own mail storage format.
support of filtering, based on length of message body. Not sure how well it copes with damned “content/alternative” messages.
Syntax of filter rules is much less cryptic and less verbose, than one of procmail. Compare
if (subject = "Foo") then save "/tmp/foo.mbox"with much more verbose procmail rule.
:0:
*^Subject:.*Foo
/tmp/foo.mboxUnfortunately, filter does not provide equivalence of two features of procmail, that are significant to my email workflow:
Matching of arbitrary header. My email provider run SpamAssassin on incoming emails and adds X-Spam-Level header. My procmail configuration uses this header to classify messages as spam. Probably, I could run SpamAssassin locally, but why bother, if settings of my email provider are fine for me.
Handling of duplicate email. In cases when people reply to me and add mailing list into carbon copy, I receive two copies of email with same Message-Id header. It is distracting.
Both filter and procmail are long dead mature. Source code of filter is twice as short, if you care about such things. Half of that is regular expression engine, that is built it modern implementations of standard C library. Give filter a shot.
Definitely, filter would benefit from some care. Use standard regular expression engine, add support for X-Spam-Level header and here it is – perfect email filtering solution. Maybe, one day, in my copious free time…